1. Field of the Invention
The present invention relates to a fuel filter apparatus for filtering contaminants from liquid fuel for combustion engines, including an indicator for displaying the condition of the filter media contained therein, and to methods of using the described apparatus. More particularly, the present invention relates to a fuel filter including a restriction indicator gauge with a visual display, for identifying when a fuel filter needs to be replaced, and to methods of using the described filter.
2. Description of the Background Art
The use of fluid filters to protect the downstream components of a machine is well known. Several different fluids associated with internal combustion engines require filtration, i.e. fuel and oil. In particular, fuel filters protect the engine from contaminants, such as dirt and water which, if left unfiltered, could result in inefficient combustion, reduced engine performance and premature engine wear. Fluid filters need to be replaced, at regular intervals, to ensure continued proper filtration.
Known fuel filters for combustion engines generally include a housing, filter, and connective conduits to provide an inlet and outlet. Known filters may also include an optional drain valve (typically a threaded plug, removable from the housing, to allow fuel or coalesced water drainage therefrom). Often, the housing is almost entirely transparent (or includes a sight glass) to permit an individual to view the condition of the fuel filter, and then determine whether replacement of the fuel filter is necessary. However, visually determining when to replace a filter, based upon this known method is subjective, given that filter replacement depends on the opinion and/or experience of the individual viewing the filter. Moreover, a plugged filter element does not always appear visually different from a clean one.
Accordingly, concerns arise on both sides as to when a fuel filter should be replaced; premature replacement of a fuel filter gives rise to cost, disposal, and environmental concerns, while delayed replacement of a fuel filter gives rise to concerns of diminished engine performance, reduced efficiency and premature wear. As a result, a number of methods and equipment for detecting deterioration and contamination of engine fuel have been developed.
Some examples of known fuel filters are illustrated in U.S. Pat. No. 4,981,584 issued to Nunes; U.S. Pat. No. 5,776,332 issued to Hurner; U.S. Pat. Nos. 5,507,942 and 5,766,449 issued to Davis, and; U.S. Pat. Nos. 5,916,442 and 6,203,698 issued to Goodrich.
The use of pressure sensors to monitor fluid pressure within fluid filters is taught by U.S. Pat. No. 4,654,140 to Chen, U.S. Pat. No. 4,818,385 to Medley, U.S. Pat. No. 5,132,009 to Futa, Jr. and U.S. Pat. No. 5,702,592 to Suri et al.
While the known devices have shown some utility for their intended purposes, a need still exists in the art for an apparatus that provides a simple, cost-effective, visual indication of the filter's condition, to reduce the subjectivity inherent in visually determining filter replacement, while still maintaining effective fuel filtration.